2-bromo - 2 - chloro-1,1,3,3-tetrafluoropropane as an inhalation anesthetic



United States Patent Olhce 3,525,794 Patented Aug. 25, 1970 3,525,794 2-BROM0 2 CHLORO-l,1,3,3-TETRAFLUORO- PROPANE AS AN INHALATION A'NESTHETIC Bernard M. Regan, Chicago, Ill., assignor to Baxter Laboratories, Inc., Morton Grove, Ill., a corporation of Delaware No Drawing. Application Aug. 31, 1967, Ser. No. 664,605, which is a continuation-in-part of application Ser. No. 538,523, Feb. 2, 1966. Divided and this application Dec. 5, 1968, Ser. No. 805,059

Int. Cl. A61k 13/00 US. Cl. 424-350 1 Claim ABSTRACT OF THE DISCLOSURE 2-bromo-2-chloro-l,1,3,3-tetrafluoropropane, useful as a nonfiammable inhalation anesthetic which is stable toward soda-lime.

This is a division of Ser. No. 664,605, filed Aug. 31, 1967, now US. Pat. 3,458,584, which in turn is a continuation'in-part of co-pending application Ser. No. 538,523, filed Feb. 2, 1966, now US. Pat. 3,362,874.

This invention relates to a novel polyhalotetrafluoropro' pane. More particularly, this invention relates to a bromochlorotetrafiuoropropane having both a bromine atom and a chlorine atom substituted on the number two carbon atom, namely, 2-bromo-2-chloro-l,1,3,3-tetraflu0- ropropane.

It is known that certain halogenated alkanes are useful inhalation anesthetics Chloroform and halothane are well-known examples of such compounds which are derivatives of the lower alkanes, methane and ethane, respectively. More recently, it has also been found that certain halogenated propanes are useful inhalation anesthetics. Thus, Muray et al., US. Pat. 3,177,260, disclose the inhalation anesthetic use of 3-bromo-3-chloro-1,1,2,2-tetrafluoropropane, which is a position isomer of the bromochlorotetrafluoropropane of the present invention.

Another position isomer of the compound of this invention also is known. Thus, Tarrant et al., 77 J. Am. Chem. Socy. 768 (1955) disclose 1-bromo-3-chloro-l,1,3,3-tetrafluoropropane. However, the latter compound is not known as an anesthetic.

It has now been found that the novel 2-bromo-2-chloro- 1,1,3,3-tetrafluoropropane of this invention is a useful nonflammable inhalation anesthetic in mice, which is more potent and has a greater inhalation margin of safety than ether, chloroform and halothane, which are in current use as inhalation anesthetics. Moreover, the novel compound of this invention is stable toward soda-lime as distinguished from the isomeric 3-bromo-3-chloro-l,1,2,2- tetrafluoropropane of Muray et al. and the isomeric lbromo-3-chloro-l,1,3,3-tetrafiuoropropane of Tarrant et al., which are not stable toward soda-lime. As such, the novel bromochlorotetrafluoropropane of this invention holds good promise as an effective and useful agent for inducing anesthesia in man, including use in conventional recirculation apparatus which employs soda lime for the absorption of carbon dioxide from the patient undergoing anesthesia.

The novel 2-bromo-2-chloro-1,1,3,3-tetrafluoropropane of the present invention is a clear liquid at normal room temperature and has a boiling point of 94 C. at 760 mm. Hg. It can be conveniently stored in containers normally used for conventional anesthetics of comparable boiling points, e.g., halothane. It is nonexplosive and nonflammable in oxygen and in air at ambient temperatures. This compound can be administered by apparatus or machines designed for the vaporization of liquid anesthetics or mixtures thereof with oxygen, air or other gaseous mixtures containing oxygen in amounts capable of supporting respiration.

For use in anesthesia, the 2-bromo-2-chloro-1,1,3,3-tetrafluoropropane should be free from toxic impurities which may be present according to the particular process used for its manufacture. This compound can, however, be used in admixture with pharmaceutically acceptable diluents and stabilizers, e.g., thymol, or one or more of the known inhalation anesthetics, e.g., nitrous oxide, ether, halothane, chloroform, cyclopropane, methoxyfluorane, and the like.

The novel bromochlorotetrafiuoropane defined herein is prepared from the novel monohalotetrafiuoropropanes disclosed and claimed in co-pending application Ser. No. 538,523, filed Feb. 2, 1966, namely, 2-chloro-1,l,3,3-tetrafluoropropane and Z-bromo-l,1,3,3-tetrafiuoropropane. This preparation can be carried out in two distinct ways:

(1) By direct substitution of hydrogen by chlorine on the number two carbon position in 2-bromo-1,1,3,3-tetrafluoropropane or (2) By elimination of this hydrogen and a fluorine from 2-chloro-l,1,3,3-tetrafluoropropane to form the intermediate cisand trans-2-chloro-1,3,3-trifluoropropanes, followed by addition of the elements BrF in proper orientation.

These two methods of preparation can be represented by the following reaction equations:

IBrF OHF4CHC1OHF alkali GHF=CC1-CHF2 In reaction (1), above, photochlorination of Z-bromo- 1,1,3,3-tetrafiuoropropane, preferably with from about 0.5 to about 1.0 molar equivalent of chlorine, produces 2-bromo-2-chloro-1,1,3,3-tetrafluoropropane, 13.7 0 94 C. which is distinguishable from the other theoretically possible monochlorination product, 2-bromo-1-chloro-1,1,3,3- tetrafluoropropane, by proton nuclear magnetic resonance spectroscopy.

In reaction (2), above, the action of soda lime or other alkaline reagents on 2-chloro-1,1,3,3-tetrafiuoropropane, preferably at a temperature of from about 25 C. to about 65 C., produces almost exclusively cisand trans-Z-chloro-1,3,3-trifluoropropenes in a proportion of about 12:1. Addition of the elements BrF to this propene mixture or to either isomer by the action of a mixture of about a onethird molar equivalent of bromine trifiuoride and about a one-third molar equivalant of bromine, preferably at a temperature of from about 30? C. to about 25 C. and in a suitable diluent, for example, l,1,2-trichloro- 1,2,2-trifluoroethane, produces 2-bromo-2-chloro-1,1,3,3- tetrafluoropropane, h 94 C., in preference to the other theoretically possible bromine trifluoride adduct, l-bromo 2-chloro-1,2,3,3-tetrafluoropropane, as shown by proton nuclear magnetic resonance spectral analysis. In this method of preparation of the novel bromochlorotetrafluoropropane of the present invention, about one molar equivalent of bromine trifiuoride can be substituted for the bromine trifluoride-brornine mixture with substantially equivalent results.

The intermediate cisand trans-2-chloro-1,3,3-trifiuoropropenes which are used to prepare the novel inhalation anesthetic defined herein also are novel compounds. They can be conveniently prepared as described above by reaction of 2-chloro-1,1,3,3-tetrafluoropropane and soda-lime or other alkaline reagents, for example, potassium hydroxide, sodium carbonate, pyridine and the like.

Although the above methods of preparation and reaction conditions are specifically described, it will be understood that the novel compounds of this invention are not limited to these specific reaction conditions or to these specific methods of preparation. For example, it will be apparent that the novel bromochlorotrifluoropropane of this invention can be prepared by bromination of 2-chloro-I,1,3,3-tetrafluoropropane in a manner analogous to the chlorination of 2-bromo-1,1,3,3-tetrafiuoropropane and by the reaction of ClF or C1F with 2-bromo-1,3,3- trifluoropropene in a manner analogous to the BrF addition to 2-chloro-1,3,3-trifluoropropenes.

The 2-bromo-1,3,3-trifluoropropenes also are novel compounds and can be conveniently prepared in a manner analogous to the preparation of the 2-chloro-1,3,3-trifluoropropenes by reaction of 2-bromo-1,1,3,3-tetrafiuoropropane and soda lime or other alkaline reagents, preferably at a temperature of from about 25 C. to about 85 C.

The preparation of the 2-bromoand 2-chloro-1,1,3,3- tetrafluoropropanes by the reaction of an alkali metal chloride and the p-toluenesulfonate ester of 1,1,3,3-tetrafluoropropan-Z-ol is disclosed in co-pending application Ser. No. 538,523, filed Feb. 2, 1966.

The following examples will further illustrate the present invention, although the invention is not limited to these specific examples. All percentages and parts herein are on a weight basis unless otherwise specified.

EXAMPLE 1 1,1,3,3-tetrafiuoropropan-2-ol (I) Hydrogen at the rate of one-half liter per minute was bubbled through 1,3dich1oro-1,1,3,3-tetrafluoroacetone at 4 C. The mixture of vapors passed through a Pyrex tube (45 cm. x 1.9 cm. I.D.) containing 2% palladium on carbon granules (4-12 mesh) and heated to 200 C. The reaction products were condensed in a trap cooled by Dry Ice. A 750:1 ration by weight of dichloro-tetrafluoroacetone to palladium is optimum.

In a typical run 1250 grams (6.28 moles) of dichlorc tetrafiuoroacetone was vaporized with hydrogen during 22 hours and the mixture passed over 85 grams of palladium carbon catalyst. Fractional distillation of the reaction products gave 704 grams (5.33 moles, 85% of theory) of crude alcohol (I) B.P. 1'06-1'09 C., suitable for use in the next step.

Alternatively, the alcohol (I) can be prepared by reduction of 1,1,3,3-tetrafiuoroacetone with sodium borohydride. The alcohol (I) obtained in this manner had B.P. 10709 C., n 1.333. The identity of the alcohols prepared in these two ways was confirmed by infrared spectra.

EXAMPLE 2 1,1,3,3-tetrafluoro-2-propyl p-toluenesulfonate (II) A mixture of crude 1,1,3,3-tetrafiuoropropan-2-o1 (I) (315 gm., 2.4 moles), p-toluenesulfonyl chloride (460 gm., 2.4 moles) and 600 ml. of water was stirred as 5 N sodium hydroxide (514 ml., 2.57 moles) was added during 1.5 hours, and the temperature was maintained between 25 C.-40 C. Stirring was continued for 16 hours. The lower layer of crude ester (II) was separated, stirred, evacuated to between 25-40 mm. Hg and heated to 125 C. until volatile impurities ceased to be removed. Five hundred eighty-three gm. (2.04 moles, 85% of theory) of crude ester (II) suitable for use in subsequent steps was obtained. Crystallization from ligroin gave II, M.P. 31 C., 21 1.466.

Analysis.--Calculated for C H F O S (percent): C, 41.91; H, 3.52, S, 11.20. Found (percent): C, 42.13; H, 3.63; S, 10.95.

4 EXAMPLE 3 2-bromo-1, 1,3 ,3-tetrafiuoropropane (III) To a stirred mixture of potassium bromide (357 gm., 3. 0 moles) in 700 ml. of diethylene glycol heated to between 200210 C. crude 1,1,3,3-tetrafluoro-2-propyl ptoluenesulfonate (II) (572 gm., 2.0 moles) was added during 1.5 hours. The vapors of III rose through a Vigreaux distilling column and descended through a coldwater spiral condensor. The liquid product was collected in an ice-cooled receiver for 1.5 hours after the addition of II was completed. It was chiefly a mixture of III, 1,4- dioxane and water, from which the III was purified by successive washings with Water and aqueous 60% sulfuric acid. It was neutralized by a wash with cold dilute aqueous sodium hydroxide. The crude bromide III amounted to 314 gm. (81.5% of theory). Fractional distillation gave 256 gm. of III, b 82.682.8 C. Pure (99.9% by G.L.C.) III has h 83 C. (1 1.8743, 11 1.3691 and a vapor pressure of 57 mm. Hg at 20 C. Its vapor pressure-temperature equation is log P=8.1690- Its 60 MC nuclear magnetic resonance (NMR) and infrared spectra confirmed the CHF CHB1'CHF structure.

EXAMPLE 4 Z-chloro-l,1,3,3-tetrafluoropr0pane (IV) In the same manner as for the bromide III, potassium chloride (81 gm., 1.07 mole), 350 ml. of diethylene glycol and crude .tosyl ester II (202.7 gm., 0.71 mole) were caused to react and the crude chloride IV (93 gm., 86% theory) was isolated after successive water washings. Fractional distillation gave 65 gm. of IV, b 64.464.7 C. Pure (99.9% by G.L.C.) IV has h 65 C., d 1.4914, 11 1.3345 and a vapor pressure of 122 mm. Hg at 20 C. Its vapor pressure-temperature equation is Its 60 MC NMR and infrared spectra confirm the CHE-CHCl-CHF structure.

EXAMPLE 5 Cisand trans-2-chloro-1,3,3-trifluoropropenes (V) A mixture of 2-chloro-1,1,3,3-tetrafluoropropane (IV) (376 gm., 2.50 moles) and low-moisture (about 2% water) soda lime (250 gm.) was heated to boiling under total reflux for eighteen hours. Ga-liquid chromatographic, infra-red, and proton nuclear magnetic resonance analyses of the liquid reaction product showed essentially complete conversion to a mixture of cisand trans-2- chloro-1,3,3-trifluoropropenes. The ratio of the cisand trans-propene isomers produced was about 12:1. The predominant propene has a longer retention time than either the other propene or the starting propane on a column packed with 20% diisodecylphthalate on Chromasorb p at C. to C. Fractional distillation of the pro pene mixture aiforded an eflicient separation of the cisand trans-isomers, with the minor isomer concentrating in the forerun. The predominant propene has D 57.7- 57.8 C., r1 1.4138, n 1.3588. Altogether 284 grams (92% yield) of cisand trans-2-chloro-1,3,3-trifluoropropenes was collected, 'b- 51.3-57.9" C., of which 227 grams had b 57.5-57.9 C. and is 99.9% the predomb nant propene isomer.

EXAMPLE 6 Cisand trans-Z-bromo-1,3,3-trifluoropropenes (VI) log P=8.0475

In the same manner as for chloride V, a mixture of 2- bromo-l,1,3,3-tetrafluoropropane (III) (368 gm., 1.88 moles) and low-moisture (about 2% Water) soda lime (180 gm.) were caused to react for about sixteen hours to produce a mixture of cisand trans-2-bromo-1,3,3-trifiuoropropenes. The ratio of the cisand trans-propene isomers produced was about 13:1. The predominant propene has a longer retention time than either the other propene or the starting propane on a column packed with 20% diisodecylphthalate on Chromasorb p at 80 C. to 100 C. Fractional distillation of the propene mixture did not afford an efiicient separation, and the cisand trans-isomers distilled concurrently, b 77.5-78.0 C. (290 gm., 1.66 moles, 88% yield). The last fraction collected afiorded the purest product, b 78.0 C., d, 1.8429, 21 1.3961, and is 99.4% the predominant propene and 0.54% the other propene.

EXAMPLE 7 2-brorno-2-chloro-1,1,3,3-tetrafiuoropropane (VII) 2-chloro-1,3,3-trifluoropropenes (V) (46.5 g., 0.355 mole) were added to a mixture of bromine trifluoride (5.9 ml., 0.12 mole), bromine (6.2 ml., 0.12 mole), and 100 ml. of 1,1,Z-trichloro-1,2,2-trifiuoroethane diluent at 7 C. in a Teflon bottle. The mixture was allowed. to warm gradually. At about 30 C. stirring of the mixture was begun with a Teflon-coated magnetic bar. An exothermic reaction subsequently ensued and the reaction mixture boiled for a short time. When the reaction subsided, the mixture was stirred for 30 minutes and then poured into a mixture of ice and water. The lower layer was separated and washed with an aqueous solution of sodium hydroxide and sodium sulfite to neutralize and decolorize the product in this layer. The lower layer was separated again, dried over anhydrous calcium chloride, and distilled to remove the diluent. The remainder (69 gm.) was fractionally distilled (from. 100 mg. of thymol) to yield a forerun, 9.5 gm., boiling 50 to 93 C.; the novel compound of this invention, 2-bromo2-chloro-1,1,3,3-tetrafluoropropane (VII), 35.4 gm., boiling 93 to 93.6"; and a 25 gm. residue. Gas-liquid chromatography showed the 35.4 gram fraction to be 98% a single component which was shown to have the CHF CBrCl-CHF structure by proton nuclear magnetic resonance spectra. Refractionation gave 2-bromo-2-chloro-l,1,3,3-tetrafiuoropropane of 99.7% purity (by G.L.C.), bo 94 C., (1 1.902.

EXAMPLE 8 2-bromo-2-chloro-1,1,3,3-tetrafluoropropane (VII) A solution of 2-chloro-1,3,3-trifiuoropropenes (V) in 1,1,2-trichloro-1,2,2-trifiuoroethane (3 ml./ gm. of propenes) is cooled to -20 C. and stirred in a Teflon bottle joined to a trap cooled to -70 C. Bromine trifluoride is added in increments through a Teflon syringe to this solu tion maintained at -20 C. until one molar equivalent (0.42 ml./gm. of propene) has been added. The reaction mixture is stirred and allowed to warm during a period of from one to three hours to C., during which time an exothermic reaction occurs. After the reaction subsides, stirring is continued for a short time and then the mixture is poured onto crushed ice. The organic layer is sep arated and then decolorized and deacidified by washing with cold aqueous sodium hydroxide solution. The washed product is separated and fractionally distilled to obtain 2- bromo-lchloro-l,1,3,3-tetrafluoropropane (VII), b 94 C., in about 40% yield.

EXAMPLE 9 2-bromo-2-chloro-l,1,3,3-tetrafluoropropane (VII) In the same manner as for the chloride in Example 8, a solution of 2-bromo-1,3,3-trifiuoropropenes (VI) in 1,- 1,2-trichloro-1,2,2-trifluoroethane (3 ml./ gm. of propenes) is cooled to -20 C. and stirred in a Teflon bottle joined to a trap cooled to -70 C. Chlorine trifluoride is slowly bubbled into this solution until one molar equivalent (0.53 gut/gm. of propene) has been added. The reaction mixture is stirred and allowed to warm to 10 C.

during a period of three hours and then poured onto crushed ice. The organic layer is separated and then decolorized and deacidified by washing with cold aqueous sodium sulfite and sodium hydroxide solutions. The washed product is separated, dried, and fractionally distilled to obtain 2-bromo-2-chloro-1,1,3,3-tetrafluoropropane (VII), b 94 C.

EXAMPLE 10 2-bromo-2-chloro-1,1,3,3-tetrafluoropropane (VII) Chlorine gas (120 gm., 1.7 moles) was bubbled at a rate of 15 grams per hour into 2-bromo-1,1,3,3-tetrafluoropropane (III) (370 gms., 1.9 moles) illuminated by 'a sun lamp through a Pyrex flask. The reaction mixture was allowed to come to a boil and reflux through a cold water condensor surmounted by a Dry Ice condenser followed by a Dry Ice cooled trap. The chlorination product was cooled, deacidified by washing with water and cold dilute aqueous sodium hydroxide solution and dried to yield a product weighing 419 grams. Gas-liquid chromatographic separation of this product on a column ten feet long and inch in diameter packed with 20% diisodecylphthalate on firebrick at 105 C. showed four components totaling 99.3% of the product. 2-bromo-2- chloro-l,1,3,3-tetrafluoropropane (VII) was identified as one of these components by its proton nuclear magnetic resonance spectrum. Its isolation by preparative gas-liquid chromatography is indicated.

EXAMPLE 11 Inhalation of the vapor of 2-bromo-2-chloro-1,1,3,3- tetrafiuoropropane admixed with air in the manner described by Robbins, 86 J. Pharmacol. Exper Therap. 197- 204 (1946), produced anesthesia in white mice. The minimum concentration by volume percent required to produce full anesthesia (loss of negative righting reflex) in 50% of the test animals in five minutes, AC and the minimum concentration by volume percent required to kill 50% of the test mice in five minutes, LC are given in Table I, below. The inhalation margin of safety as measured in mice by the ratio LC /AC is also given in Table I. For purposes of comparison, similar data which were obtained under the same conditions as for the above compound are given for three inhalation anesthetics in current use, namely, ether, chloroform, and halothane. The number of mice used with the different anesthetic agents varied from 25 to 92 for determining each of the AC and LC doses.

The results set forth in the above table show that the novel bromochlorotetrafluoropropane of this invention is more potent and has a greater inhalation margin of safety than the three inhalation anesthetics in current use.

EXAMPLE 12 The soda lime stability of the novel inhalation anesthetic of the present invention was determined essentially according to the procedure of Glover and Hodgson, 16 Anesthesia 19-23 (1961). The liquid anesthetic (0.65 ml.) and soda lime (0.50 gm., 8-12 mesh, 15%20% by weight of water) were sealed in a glass ampule and heated at 70 C. for three hours and then analyzed by gas-liquid partition chromatography. For purposes of comparison, a liquid anesthetic blank was treated in the same Way in the absence of soda lime. The chromatographic results are given in Table II, below, in which R.T. is retention time in minutes from air and Area percent is times the ratio of the area under a peak to the total area under The remarkable soda lime stability of the novel bromochlorotetrafluoropropane of this invention is shown by the high correspondences between the 99.7 and 99.3 Area percents after 2.9minutes of retention time in the blank sample and the soda lime treated sample, respectively.

What is claimed is:

1. The method of inducing anesthesia in an animal which comprises administering by inhalation to said animal and inhalation anesthetic effective amount of 2-br0- 1 mo-2-chloro-1,1,3,3-tetrafluoropropane.

TABLE II.SODA LIME STABILITY OF ANES'THETICS Blank Soda Lime Treated Area, Area, Area, Area, Compound R.T. percent RT. percent Rfl. percent RIP. percent CHFz-CBrCl-CHF2 2. 9 99. 7 0. 98 0.23 1. 0 0. 13 2. 9 99 3 CHFz-GFzCHBrC1 10. 4 96. 7 8. 5 58. 5 10. 4 38. 3 Halothane 7. 2 99. 9+ 4. 2 0.20 7 2 99. 8

References Cited UNITED STATES PATENTS 3,177,260 4/1965 Muray et al. 260653 3,332,840 7/1967 Regan 260653 3,362,874 2/ 1968 Regan 424350 ALBERT T. MEYERS, Primary Examiner J. D. GOLDBERG, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3, 525, 794 Dated August 25, 1970 Bernard M. Regan It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the specification, at col. 2, line 37, cancel "CHF and insert -CHF Signed and sealed this 20th day of April 1971.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

EDWARD PLFLPJTCH-EmJR.

Commissioner of Patents Attesting Officer USCOMM-DC GO376-P69 FORM PO-IDSO (10-69) u s. oovumntm "lunar. ornc! nu o-ui-nn 

